The use of liquid (emulsion) polyelectrolytes in water, wastewater and papermaking applications began to proliferate in the early 1980's. Polyelectrolytes are useful for removing fine particulate matter from water.
Initially, traditional batch systems were used to dilute and activate the new polyelectrolytes, commonly called polymers. Typical batch systems use one or more 50-5000 gallon tanks. A measured amount of polymer in an oil-based emulsion is dumped or pumped into the tanks, which contain water, with a propeller mixer running. The mixing action of the propeller strips some of the oil from the polymer molecules, called inversion, allowing the molecules to absorb water. After some period of time (10-30 min.) the mixer is turned off and the solution is allowed to “age” for an additional 30-60 minutes. Aging allows the polymer molecules to open and extend, called activation, exposing ionic sites to the water.
After aging, the solution is dosed into water containing suspended solids. The ionic sites attract and grasp suspended particles in the water, and the particles settle to the bottom of the water, leaving the water in a cleaner condition. Batch systems have several problems, though. Inversion is incomplete, and the impact of the propeller damages many of the polymer molecules. Activation is slow and cumbersome, and the process is inefficient overall.
In-line systems for activating the new liquid polymers began to appear in about 1982 and gained fairly rapid acceptance in the marketplace. In-line systems invert the emulsion and activate the polymer, fairly continuously moving the inverted solution until it leaves the system. In-line systems do not use aging tanks and offer savings in space required, installed cost and cost of operation. While they address some of the problems found in batch systems, though, they only solve them to some extent, as the shear forces they create lack uniformity, which limits the degree of activation achieved.
Thus, there is a need for a polymer mixing apparatus that more uniformly inverts an oil-phase continuous polymer emulsion to a water phase continuous emulsion, more fully exposing the polymer molecules to activating water.
Accordingly, one object of this invention is to provide new and improved polymer mixing devices.
Another object is to provide new and improved polymer mixing devices that more fully and uniformly strip oil from polymers, which allows the polymer to hydrate in an aqueous solution.
Still another object is to provide new and improved polymer mixing devices which cause less damage to the polymer molecules in the process of inversion and activation.